Rotary screw compressors use two lobed rotating and closely meshing rotors that alternatively draw gas fluid into the mesh. The gas fluid is then compressed, and expelled through a discharge opening at a higher-pressure level. A differential pressure is developed across the compressor such that when the compressor shuts down, gas can flow back through the compressor if the gas flow is not restricted in some way. This backflow is not usually desirable and as such, devices such as check valves are placed in the suction or discharge line of the compressor to prevent this backflow of gas from occurring at shutdown. However, these check valve devices can be very expensive and bulky. Backflow in a screw compressor produces undesirable high rotor speeds, where in some cases maximum bearing speeds of the rotor are exceeded. The excessive speeds cause loud noise levels that are not only annoying and unnecessary, but are unacceptable in many situations.
In addition to preventing the backflow in the compressor, in rotary screw compressors it is necessary and favorable to protect the sensitive internal components from system dirt by providing a fine mesh strainer in the compressor's suction line. To accommodate the protection of the components, the strainer must be placed in the casting/suction piping for the compressor.
Thus, what is needed is one device that can prevent backflow of gas fluid and protect the compressor components from system dirt debris while having a reduced size compared to the traditional expensive, bulky systems.